title = "Extending databases to precision-controlled retrieval of qualitative information",

abstract = "A hierarchy is an arrangement of qualitative values in a tree with certain properties. Hierarchies allow to define the confusion conf(r, s) in using qualitative value r instead of the intended or correct value s. From here, {"}predicate P holds for object o{"}, written P(o), is generalized to {"}P holds for o within confusion ε{"}, written Pε(o) . These precision-controlled predicates are useful to retrieve approximate answers, where the error (confusion) is known. The predicates are implemented through an extended SQL that uses confusion to retrieve information from a database. We show how to extend any database for precision-controlled retrieval. Limiting the total error is also useful, and this is achieved by predicate Pε. Examples are given. {\textcopyright} Springer-Verlag Berlin Heidelberg 2005.",